Congestive heart failure (CHF) is the most common cause of hospitalization among Americans aged 65 and older. Incidence and prevalence of CHF are increasing because of aging of the population and increased survival following myocardial infarction. Diet patterns and food choices may influence risk of CHF through myocardial infarction, hypertension, and diabetes or through more subtle metabolic disturbances. Dietary interventions have the potential to augment currently available behavioral and pharmacologic CHF prevention strategies, but currently little is known about the relationship between diet and CHF. We have developed three hypotheses regarding diet patterns and CHF: 1) Adherence to the DASH diet will reduce incidence of CHF in women and men;2) Consumption of fatty fish, total omega-3 polyunsaturated fatty acids, and marine and plant derived omega-3 polyunsaturated fatty acids will reduce incidence of CHF in women and men;higher omega-6 to omega-3 ratio will be associated with increased risk;and 3) Higher dietary glycemic index and dietary glycemic load will be associated with increased risk of CHF in women. To evaluate these hypotheses, we will conduct a prospective study in the context of two well-characterized cohorts: the Swedish Mammography Cohort of over 36,000 women and the Cohort of Swedish Men which includes over 45,000 men. In these cohorts, diet was measured using validated food-frequency questionnaires. Individuals were followed from January 1, 1998 to December 31, 2003 through the Swedish inpatient and cause-of-death registers for first hospitalization due to or death from CHF, a diagnosis that has been shown to have high validity. We will use proportional hazards models to calculate incidence rate ratios of CHF associated with the dietary patterns. Plain language summary: Congestive heart failure is a common and often deadly disease, particularly among older adults. Currently little is known about dietary causes of congestive heart failure. We will evaluate whether adherence to the DASH diet, fatty fish and polyunsaturated fatty acids, and dietary glycemic index and glycemic load affect risk of congestive heart failure in two large groups, 36,000 women in the Swedish Mammography Cohort and 45,000 men in the Cohort of Swedish Men.